Downlink and synchronization techniques for narrowband wireless communications

ABSTRACT

Various techniques for narrowband communications in a wireless communications network are provided. Narrowband communications may be transmitted using a single resource block (RB) of a number of RBs used for wideband communications. In order to provide for efficient device discovery and synchronization using narrowband communications, a synchronization signal, such as a primary synchronization signal (PSS) or secondary synchronization signal (SSS), may be transmitted within the single resource block. The synchronization signal may be transmitted, for example, using multiple orthogonal frequency division multiplexing (OFDM) symbols within the single RB. A common reference signal (CRS) may also be present in the single resource block, which may puncture the synchronization signal, in some examples. In other examples, the synchronization signal may be mapped to non-CRS symbols of the single resource block.

CROSS REFERENCES

The present Application for Patent is a Divisional of U.S. patentapplication Ser. No. 15/244,653 by Rico Alvarino, et al., entitled“Downlink and Synchronization Techniques for Narrowband WirelessCommunications” filed Aug. 23, 2016, which claims priority to U.S.Provisional Patent Application No. 62/210,343 by Rico Alvarino et al.,entitled “Downlink and Synchronization Techniques for NarrowbandWireless Communications,” filed Aug. 26, 2015; and U.S. ProvisionalPatent Application No. 62/277,462 by Rico Alvarino et al., entitled“Downlink and Synchronization Techniques for Narrowband WirelessCommunications,” filed Jan. 11, 2016; each of which is assigned to theassignee hereof, and expressly incorporated herein.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to downlink and synchronization techniques for narrowbandwireless communications.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system). A wireless multiple-access communications system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UE).

Some wireless communications systems may provide for narrowbandcommunication between wireless devices, such as those implementingMachine-to-Machine (M2M) communication or Machine Type Communication(MTC). In some examples, MTC devices may have reduced complexity orreduced performance metrics and may be associated with narrowbandcommunication, low cost operation, low power consumption, or the like.Signal processing using sampling rates appropriate for non-MTC devicesmay result in high processing complexity and power consumption relativeto the capabilities of an MTC device.

SUMMARY

The described features generally relate to one or more improved systems,methods, and/or apparatuses for narrowband communication in a wirelesscommunications system. In some aspects, a synchronization signal, suchas a primary synchronization signal (PSS) or secondary synchronizationsignal (SSS) may be transmitted within a single resource block in anarrowband transmission. A common reference signal (CRS) (also referredto as a cell-specific reference signal) may also be present in thesingle resource block, which may puncture the synchronization signal, insome examples. In other examples, the synchronization signal may bemapped to non-CRS symbols of the single resource block.

In certain aspects of the disclosure, a base station may transmit, and aUE may receive, an indication of a location of a single resource blockfor narrowband transmissions within a wideband region of the systembandwidth. The UE may identify one or more synchronization parametersfor receiving the narrowband transmissions based on the indication. TheUE may, in some examples, select a decoding technique for decoding basedon the identified frequency band of the narrowband transmissions, suchas based on whether the identified frequency band is within a widebandtransmission bandwidth or outside of the wideband transmissionbandwidth. In other aspects, a set of subcarriers may be identifiedwithin the narrowband region of the system bandwidth used to transmit aresource block, and a center-frequency subcarrier of the set ofsubcarriers identified. One or more other subcarriers of the set ofsubcarriers may be modified based on the identification of thecenter-frequency subcarrier, such as through frequency shifting or powerboosting, for example.

A method of wireless communication is described. The method may includereceiving a synchronization signal for device discovery, thesynchronization signal comprising two or more OFDM symbols within asingle resource block transmitted in the narrowband region, andsynchronizing one or more parameters of transmissions in the narrowbandregion based at least in part on the synchronization signal.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving a synchronization signal for devicediscovery, the synchronization signal comprising two or more OFDMsymbols within a single resource block transmitted in the narrowbandregion, and means for synchronizing one or more parameters oftransmissions in the narrowband region based at least in part on thesynchronization signal.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to receive asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource blocktransmitted in the narrowband region, and synchronize one or moreparameters of transmissions in the narrowband region based at least inpart on the synchronization signal.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto receive a synchronization signal for device discovery, thesynchronization signal comprising two or more OFDM symbols within asingle resource block transmitted in the narrowband region, andsynchronize one or more parameters of transmissions in the narrowbandregion based at least in part on the synchronization signal.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for determining whether the narrowbandregion is within a bandwidth of one or more wideband transmissions basedat least in part of a format of the synchronization signal. Additionallyor alternatively, in some examples the determining comprises identifyingthat the narrowband region is within the bandwidth of one or morewideband transmissions in response to the synchronization signal beingformatted in consecutive OFDM symbols within the single resource block,and identifying that the narrowband region is outside of the bandwidthof one or more wideband transmissions in response to the synchronizationsignal being formatted in one or more non-consecutive OFDM symbolswithin the single resource block.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the synchronization signalcomprises one or more of a PSS or an SSS. Additionally or alternatively,in some examples the generating the synchronization signal comprisesgenerating a sequence in a frequency domain or a time domain based atleast in part on a number of OFDM symbols in the single resource block,and generating an interpolated time domain version of the first sequencebased at least in part on a set of samples of the first sequence.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the generating thesynchronization signal further comprises splitting the interpolated timedomain version into a plurality of parts each having a duration of oneOFDM symbol, identifying a subset of samples for each part thatcorrespond to a cyclic prefix associated with the associated OFDMsymbol, removing the identified subset of samples for each part, andinserting a cyclic prefix into each part. Additionally or alternatively,in some examples generating the synchronization signal further compriseswindowing each OFDM symbol in the frequency domain such that only asubset of OFDM subcarriers carry the synchronization sequence.

A method of wireless communication is described. The method may includereceiving an indication of a location of a single resource block fornarrowband transmissions, the single resource block within the widebandregion of the system bandwidth, and identifying one or moresynchronization parameters for receiving the narrowband transmissionsbased at least in part on the indication.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving an indication of a location of a singleresource block for narrowband transmissions, the single resource blockwithin the wideband region of the system bandwidth, and means foridentifying one or more synchronization parameters for receiving thenarrowband transmissions based at least in part on the indication.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to receive anindication of a location of a single resource block for narrowbandtransmissions, the single resource block within the wideband region ofthe system bandwidth, and identify one or more synchronizationparameters for receiving the narrowband transmissions based at least inpart on the indication.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto receive an indication of a location of a single resource block fornarrowband transmissions, the single resource block within the widebandregion of the system bandwidth, and identify one or more synchronizationparameters for receiving the narrowband transmissions based at least inpart on the indication.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the identifying the one ormore synchronization parameters comprises generating a CRS sequencebased at least in part on the a cell identification of a transmitter anda resource block offset value included in the indication. Additionallyor alternatively, in some examples the indication comprises a totalwideband bandwidth of the system bandwidth and a resource block indexthat indicates a location of the single resource block.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the indication is transmittedin one or more of a master information block (MIB) or a systeminformation block (SIB).

A method of wireless communication is described. The method may includeidentifying a frequency band of the narrowband region of the systembandwidth for transmission of a physical broadcast channel (PBCH) thatincludes system information for device discovery, and selecting adecoding technique for decoding the PBCH based at least in part on theidentified frequency band of the narrowband region.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying a frequency band of the narrowband regionof the system bandwidth for transmission of a PBCH that includes systeminformation for device discovery, and means for selecting a decodingtechnique for decoding the PBCH based at least in part on the identifiedfrequency band of the narrowband region.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to identify afrequency band of the narrowband region of the system bandwidth fortransmission of a PBCH that includes system information for devicediscovery, and select a decoding technique for decoding the PBCH basedat least in part on the identified frequency band of the narrowbandregion.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto identify a frequency band of the narrowband region of the systembandwidth for transmission of a PBCH that includes system informationfor device discovery, and select a decoding technique for decoding thePBCH based at least in part on the identified frequency band of thenarrowband region.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for determining, based at least in parton the identified frequency band, whether the narrowband region iswithin a bandwidth of one or more wideband transmissions. Additionallyor alternatively, in some examples the determining whether thenarrowband region is within the bandwidth of one or more widebandtransmissions is based at least in part on a radio access technologyassociated with the identified frequency band.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the determining whether thenarrowband region is within the bandwidth of one or more widebandtransmissions comprises determining that the narrowband region isoutside of the bandwidth of one or more wideband transmissions inresponse to the identified frequency band being located in radiospectrum allocated to Global System for Mobile communications (GSM)communications, and determining that the narrowband region is within thebandwidth of one or more wideband transmissions in response to theidentified frequency band being located in radio spectrum allocated toLTE communications. Additionally or alternatively, in some examplesselecting the decoding technique for decoding the PBCH comprisesselecting a CRS based decoding technique in response to determining thatthe narrowband region is outside of the bandwidth of one or morewideband transmissions, and selecting a demodulation reference signal(DMRS) based decoding technique in response to determining that thenarrowband region is within the bandwidth of one or more widebandtransmissions.

A method of wireless communication is described. The method may includeidentifying a plurality of subcarriers within the narrowband region ofthe system bandwidth used to transmit a resource block, identifying acenter-frequency subcarrier of the plurality of subcarriers used totransmit the resource block, and modifying one or more other subcarriersof the plurality of subcarriers based at least in part on theidentification of the center-frequency subcarrier.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying a plurality of subcarriers within thenarrowband region of the system bandwidth used to transmit a resourceblock, means for identifying a center-frequency subcarrier of theplurality of subcarriers used to transmit the resource block, and meansfor modifying one or more other subcarriers of the plurality ofsubcarriers based at least in part on the identification of thecenter-frequency subcarrier.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to identify aplurality of subcarriers within the narrowband region of the systembandwidth used to transmit a resource block, identify a center-frequencysubcarrier of the plurality of subcarriers used to transmit the resourceblock, and modify one or more other subcarriers of the plurality ofsubcarriers based at least in part on the identification of thecenter-frequency subcarrier.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto identify a plurality of subcarriers within the narrowband region ofthe system bandwidth used to transmit a resource block, identify acenter-frequency subcarrier of the plurality of subcarriers used totransmit the resource block, and modify one or more other subcarriers ofthe plurality of subcarriers based at least in part on theidentification of the center-frequency subcarrier.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the modifying one or moreother subcarriers comprises receiving an indication that thecenter-frequency subcarrier is to be unused for data transmissions, andrating matching data transmissions around the center-frequencysubcarrier. Additionally or alternatively, in some examples themodifying one or more other subcarriers further comprises power boostingone or more of the plurality of subcarriers other than thecenter-frequency subcarrier.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the modifying one or moreother subcarriers comprises applying a frequency shift to one or more ofthe plurality of subcarriers other than the center-frequency subcarrier.Additionally or alternatively, in some examples the modifying one ormore other subcarriers comprises generating a digital waveform with anoffset corresponding to a frequency shift of one-half of a subcarrierfrequency bandwidth, and adjusting a transmit oscillator based at leastin part on the offset of the digital waveform.

A method of wireless communication is described. The method may includegenerating a synchronization signal for device discovery, thesynchronization signal comprising two or more OFDM symbols within asingle resource block, and transmitting the synchronization signal inthe narrowband region.

An apparatus for wireless communication is described. The apparatus mayinclude means for generating a synchronization signal for devicediscovery, the synchronization signal comprising two or more OFDMsymbols within a single resource block, and means for transmitting thesynchronization signal in the narrowband region.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to generate asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource block, andtransmit the synchronization signal in the narrowband region.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto generate a synchronization signal for device discovery, thesynchronization signal comprising two or more OFDM symbols within asingle resource block, and transmit the synchronization signal in thenarrowband region.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the synchronization signalcomprises one or more of a PSS or a SSS. Additionally or alternatively,in some examples the synchronization signal is transmitted in a set ofcontiguous OFDM symbols.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for transmitting a CRS using one ormore resource elements (REs) that puncture the set of contiguous OFDMsymbols. Additionally or alternatively, some examples may includeprocesses, features, means, or instructions for identifying one or moreOFDM symbols within the single resource block as CRS OFDM symbols thatinclude one or more CRS REs, and mapping the OFDM symbols that containthe synchronization signal to non-CRS OFDM symbols.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the transmission of thesynchronization signal in the narrowband region comprises transmittingthe synchronization signal in a subframe previously configured as a MBMSsingle frequency network (MBSFN) subframe. Additionally oralternatively, some examples may include processes, features, means, orinstructions for configuring a subframe that includes thesynchronization signal as an MBSFN subframe.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for identifying whether the narrowbandregion is within a bandwidth of one or more wideband transmissions, andindicating to one or more receivers whether the narrowband region iswithin the bandwidth of one or more wideband transmissions. Additionallyor alternatively, in some examples the indicating to one or morereceivers whether the narrowband region is within the bandwidth of oneor more wideband transmissions comprises selecting OFDM symbols withinthe single resource block for transmission of the based at least in parton whether the narrowband region is within the bandwidth of one or morewideband transmissions, and transmitting the synchronization signalusing the selected OFDM symbols.

A method of wireless communication is described. The method may includeidentifying a location of the narrowband region of the system bandwidthas a single resource block within a wideband region of the systembandwidth, and transmitting an indication of the location of the singleresource block within the wideband region of the system bandwidth.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying a location of the narrowband region of thesystem bandwidth as a single resource block within a wideband region ofthe system bandwidth, and means for transmitting an indication of thelocation of the single resource block within the wideband region of thesystem bandwidth.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to identify alocation of the narrowband region of the system bandwidth as a singleresource block within a wideband region of the system bandwidth, andtransmit an indication of the location of the single resource blockwithin the wideband region of the system bandwidth.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto identify a location of the narrowband region of the system bandwidthas a single resource block within a wideband region of the systembandwidth, and transmit an indication of the location of the singleresource block within the wideband region of the system bandwidth.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the indication comprises atotal wideband bandwidth of the system bandwidth and a resource blockindex that indicates a location of the single resource block.Additionally or alternatively, in some examples the indication comprisesa resource block offset from start of a wideband bandwidth of the systembandwidth. In further examples, the resource block offset is offset withrespect to the center of the bandwidth.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the indication comprises oneor more CRS resource elements included in the single resource block.Additionally or alternatively, in some examples the indication istransmitted in one or more of a MIB or a SIB.

A method of wireless communication is described. The method may includegenerating a PBCH signal for transmission of system information fordevice discovery in the narrowband region, modulating the PBCH signalbased at least in part on a DMRS, and transmitting the modulated PBCHsignal in the narrowband region.

An apparatus for wireless communication is described. The apparatus mayinclude means for generating a PBCH signal for transmission of systeminformation for device discovery in the narrowband region, means formodulating the PBCH signal based at least in part on a DMRS, and meansfor transmitting the modulated PBCH signal in the narrowband region.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to generate aPBCH signal for transmission of system information for device discoveryin the narrowband region, modulate the PBCH signal based at least inpart on a DMRS, and transmit the modulated PBCH signal in the narrowbandregion.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto generate a PBCH signal for transmission of system information fordevice discovery in the narrowband region, modulate the PBCH signalbased at least in part on a DMRS, and transmit the modulated PBCH signalin the narrowband region.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the modulating the PBCHsignal comprises selecting a precoding matrix for transmission of themodulated PBCH signal, and using the selected precoding matrix for othertransmissions in the narrowband region on the system bandwidth.Additionally or alternatively, some examples may include processes,features, means, or instructions for transmitting a CRS in one or moreof the modulated PBCH signal or the other transmissions in thenarrowband region of the system bandwidth, the CRS for use in channelestimation be one or more receivers.

A method of wireless communication is described. The method may includegenerating a PBCH signal for transmission of system information fordevice discovery, the PBCH signal included in a resource block to betransmitted in the narrowband region, identifying a subframe thatincludes the resource block as a MBSFN subframe, and transmitting thePBCH signal in the MBSFN subframe.

An apparatus for wireless communication is described. The apparatus mayinclude means for generating a PBCH signal for transmission of systeminformation for device discovery, the PBCH signal included in a resourceblock to be transmitted in the narrowband region, means for identifyinga subframe that includes the resource block as a MBSFN subframe, andmeans for transmitting the PBCH signal in the MBSFN subframe.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to generate aPBCH signal for transmission of system information for device discovery,the PBCH signal included in a resource block to be transmitted in thenarrowband region, identify a subframe that includes the resource blockas a MBSFN subframe, and transmit the PBCH signal in the MBSFN subframe.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto generate a PBCH signal for transmission of system information fordevice discovery, the PBCH signal included in a resource block to betransmitted in the narrowband region, identify a subframe that includesthe resource block as a MBSFN subframe, and transmit the PBCH signal inthe MBSFN subframe.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for transmitting a CRS in the resourceblock. Additionally or alternatively, in some examples the CRS isgenerated assuming a resource block offset of zero.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the CRS is transmitted in oneor more OFDM symbols within the resource block, and wherein the one ormore OFDM symbols have a fixed offset within the resource block.

Further scope of the applicability of the described methods andapparatuses will become apparent from the following detaileddescription, claims, and drawings. The detailed description and specificexamples are given by way of illustration only, since various changesand modifications within the spirit and scope of the description willbecome apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 illustrates an example of a wireless communications system thatsupports downlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure;

FIG. 2 illustrates an example of a wireless communications subsystemthat supports downlink and synchronization techniques for narrowbandwireless communications in accordance with various aspects of thepresent disclosure;

FIG. 3 illustrates an example of a system bandwidth and various optionsfor placement of a narrowband transmission resource block within asystem bandwidth that support downlink and synchronization techniquesfor narrowband wireless communications, in accordance with variousaspects of the present disclosure;

FIG. 4 illustrates an example of a resource element mapping thatsupports downlink and synchronization techniques for narrowband wirelesscommunications, in accordance with various aspects of the presentdisclosure;

FIG. 5 illustrates another example of a resource element mapping thatsupports downlink and synchronization techniques for narrowband wirelesscommunications, in accordance with various aspects of the presentdisclosure;

FIG. 6 illustrates an example of a narrowband region within atransmission bandwidth of a wideband transmission and a narrowbandregion in another allocated frequency band support downlink andsynchronization techniques for narrowband wireless communications, inaccordance with various aspects of the present disclosure;

FIG. 7 illustrates an example of a different center frequencysub-carriers for a wideband transmission and a narrowband transmission,in accordance with various aspects of the present disclosure;

FIGS. 8A-8C illustrate examples of a sequence generation that supportsdownlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure;

FIG. 9 illustrates an example of cross-correlation properties of anexemplary sequence generated in accordance with various aspects of thepresent disclosure;

FIGS. 10-13 illustrate examples of process flows that support downlinkand synchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure;

FIGS. 14-16 show block diagrams of a wireless device that supportsdownlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure;

FIG. 17 illustrates a block diagram of a system including a UE thatsupports downlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure;

FIGS. 18-20 show block diagrams of a wireless device that supportsdownlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure;

FIG. 21 illustrates a block diagram of a system including a base stationthat supports downlink and synchronization techniques for narrowbandwireless communications in accordance with various aspects of thepresent disclosure; and

FIGS. 22-29 illustrate methods for downlink and synchronizationtechniques for narrowband wireless communications in accordance withvarious aspects of the present disclosure.

DETAILED DESCRIPTION

Techniques are described for M2M communication that may utilize anarrowband region of a system operating frequency bandwidth. M2Mcommunication or MTC refers to data communication technologies thatallow automated devices to communicate with one another with little orno human intervention. For example, M2M and/or MTC may refer tocommunications from a device that integrate sensors or meters to measureor capture information and relay that information to a central server orapplication program that can make use of the information or present theinformation to humans interacting with the program or application. Sucha device may be called a M2M device, an MTC device and/or an MTC UE. Insome cases, networks of MTC devices communicating to each other or oneor more servers may be referred to as the Internet of Things (IoT). Ininstances where the communication is performed over a cellular network,this may be referred to as a Cellular IoT (CIoT). In some deployments,CIoT devices may communicate using a relatively small portion ofallocated bandwidth of a cellular network, which may be referred to asnarrowband communication. Other portions of the allocated bandwidth, orsystem bandwidth, of the cellular network may be used for communicationsthat have higher data rates and are referred to as widebandcommunications herein. In some examples, the narrowband communicationsmay occupy 200 kHz of a radio frequency spectrum band, as compared to1.4 MHz to 20 MHz system bandwidth.

In some deployments, CIoT devices may have a 164 dB Minimum CouplingLoss (MCL), which may be achieved through relatively high power spectraldensity (PSD). CIoT devices may have relatively high power efficiencyrequirements, and CIoT networks may routinely support a relatively largenumber of devices (e.g., a relatively large number of water meters, gasmeters, electric meters in a given area). CIoT devices may be designedto have a relatively low cost as well, and thus may have hardwarecomponents that are specifically designed to operate in a powerefficient manner and that do not have a significant amount of processingcapabilities beyond what may be needed for narrowband communications. Asmentioned above, in some deployments such MTC devices may operate with a200 kHz channelization.

Various aspects of the disclosure provide techniques for narrowbandcommunications in an LTE wireless communications network. In someaspects, narrowband MTC communications may be transmitted using a singleresource block (RB) of a number of RBs used for wideband LTEcommunications. A UE using narrowband communications, however, may needto perform cell search within the single RB narrowband, and the signalsused for search (PSS/SSS/PBCH) may need to be redesigned for single RBsignaling. Further, since the single RB narrowband region may be usedwithin a legacy wideband LTE region, some legacy LTE signals may need tobe transmitted even within the narrowband region, such as CRS or legacycontrol region, which may interfere with the cell search signals.Whether the narrowband region is stand-alone or contained within awideband region, these factors may impact the design for initial accessfor narrowband LTE. Further, the narrowband initial access design may betailored for compatibility with both a stand-alone narrowband region anda narrowband region within a legacy wideband region.

In order to provide for efficient device discovery and synchronizationusing narrowband communications, some aspects provide a synchronizationsignal, such as a PSS or an SSS, that is transmitted within the singleresource block. The synchronization signal may be transmitted, forexample, using multiple orthogonal frequency division multiplexing(OFDM) symbols within the single RB. A CRS may also be present in thesingle resource block, which may puncture the synchronization signal, insome examples. In other examples, the synchronization signal may bemapped to non-CRS symbols of the single resource block.

In certain aspects of the disclosure, a base station may transmit, and aUE may receive, an indication of a location of the single resource blockfor narrowband transmissions within a wideband region of the systembandwidth. The UE may identify one or more synchronization parametersfor receiving the narrowband transmissions based on the indication. TheUE may, in some examples, select a decoding technique for decoding basedon the identified frequency band of the narrowband transmissions, suchas based on whether the identified frequency band is within a widebandtransmission bandwidth or outside of the wideband transmissionbandwidth. In other aspects, a set of subcarriers may be identifiedwithin the narrowband region of the system bandwidth used to transmit aresource block, and a center-frequency subcarrier of the set ofsubcarriers identified. One or more other subcarriers of the set ofsubcarriers may be modified based on the identification of thecenter-frequency subcarrier, such as through frequency shifting or powerboosting, for example.

Aspects of the disclosure are initially described in the context of awireless communication system. Specific examples are then described fornarrowband MTC communications in an LTE system. These and other aspectsof the disclosure are further illustrated by and described withreference to apparatus diagrams, system diagrams, and flowcharts thatrelate to downlink and synchronization techniques for narrowbandwireless communications.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be an LTE/LTE-Advanced (LTE-A) network.

The base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink (UL) transmissions from a UE 115 to a base station 105,or downlink (DL) transmissions, from a base station 105 to a UE 115. UEs115 may be dispersed throughout the wireless communications system 100,and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile station, a subscriber station, a remote unit, awireless device, an access terminal, a handset, a user agent, a client,or some other suitable terminology. A UE 115 may also be a cellularphone, a wireless modem, a handheld device, a personal computer, atablet, a personal electronic device, an MTC device or the like.

The base stations 105 may communicate with the core network 130 and withone another. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller. In some examples, base stations 105 may be macrocells, small cells, hot spots, or the like. Base stations 105 may alsobe referred to as eNodeBs (eNBs) 105.

As mentioned above, some types of wireless devices may provide forautomated communication. Automated wireless devices may include thoseimplementing M2M communication or MTC. M2M or MTC may refer to datacommunication technologies that allow devices to communicate with oneanother or a base station 105 without human intervention. For example,M2M or MTC may refer to communications from devices that integratesensors or meters to measure or capture information and relay thatinformation to a central server or application program that can make useof the information or present the information to humans interacting withthe program or application. Some UEs 115 may be MTC devices, such asthose designed to collect information or enable automated behavior ofmachines. Examples of applications for MTC devices include smartmetering, smart switches, inventory monitoring, water level monitoring,equipment monitoring, healthcare monitoring, wildlife monitoring,weather and geological event monitoring, fleet management and tracking,remote security sensing, physical access control, and transaction-basedbusiness charging, to name but a few examples. An MTC device may operateusing half-duplex (one-way) communications at a reduced peak rate. MTCdevices may also be configured to enter a power saving “deep sleep” modewhen not engaging in active communications. According to various aspectsof the present disclosure, MTC devices may operate using narrowbandcommunications that may be located within a bandwidth of other widebandcommunications or outside of the bandwidth of other widebandcommunications.

As mentioned above, various aspects of the disclosure provide techniquesfor device discovery and synchronization using narrowbandcommunications. In some examples, a UE 115 attempting to access awireless network may perform an initial cell search by detecting a PSSfrom a base station 105. The PSS may enable synchronization of slottiming and may indicate a physical layer identity value. The UE 115 maythen detect an SSS. The SSS may enable radio frame synchronization, andmay provide a cell identity value, which may be combined with thephysical layer identity value to identify the cell. The SSS may alsoenable detection of a duplexing mode and a cyclic prefix length. Somesystems, such as time division duplex (TDD) systems, may transmit an SSSbut not a PSS. Both the PSS and the SSS, according to establishedwideband techniques, may be located in the central 62 and 72 subcarriersof a carrier, respectively.

In certain aspects of the present disclosure, the PSS and the SSS may belocated within a single RB, and may occupy multiple OFDM symbols of thesingle resource block in which they are transmitted, as compared to somewideband deployments that may have a single OFDM symbol with PSS or SSSwithin a single RB. After receiving the PSS and SSS, the UE 115 mayreceive a MIB, which may be transmitted in a PBCH. The MIB may containsystem bandwidth information, a system frame number (SFN), and aphysical HARQ indicator channel (PHICH) configuration. After decodingthe MIB, the UE 115 may receive one or more SIBs. For example, SIB1 maycontain cell access parameters and scheduling information for other Ms.Decoding SIB1 may enable the UE 115 to receive SIB2. SIB2 may containradio resource control (RRC) configuration information related to randomaccess channel (RACH) procedures, paging, physical uplink controlchannel (PUCCH), physical uplink shared channel (PUSCH), power control,SRS, and cell barring. After completing initial cell synchronization, aUE 115 may decode the MIB, SIB1 and SIB2 prior to accessing the network.The MIB may be transmitted on PBCH and may carry a few important piecesof information for UE initial access, including: downlink (DL) channelbandwidth in term of RBs, PHICH configuration (duration and resourceassignment), and SFN. A new MIB may be broadcast periodically andrebroadcast every frame (10 ms). After receiving the MIB, a UE mayreceive one or more SIBs. Different SIBs may be defined according to thetype of system information conveyed. SIB1 may include accessinformation, including cell identity information, and it may indicatewhether a UE is allowed to camp on a cell 105. SIB1 may also includescell selection information (or cell selection parameters). Additionally,SIB1 includes scheduling information for other Ms. SIB2 may be scheduleddynamically according to information in SIB1, and may include accessinformation and parameters related to common and shared channels. Theperiodicity of SIB2 can be set to, for example, 8, 16, 32, 64, 128, 256or 512 radio frames.

LTE systems may utilize OFDMA on the DL and single carrier frequencydivision multiple access (SC-FDMA) on the UL. OFDMA and SC-FDMApartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones or bins. Each subcarriermay be modulated with data. The spacing between adjacent subcarriers maybe fixed, and the total number of subcarriers (K) may be dependent onthe system bandwidth. For example, K may be equal to 72, 180, 300, 600,900, or 1200 with a subcarrier spacing of 15 kilohertz (KHz) for acorresponding system bandwidth (with guardband) of 1.4, 3, 5, 10, 15, or20 megahertz (MHz), respectively. The system bandwidth may also bepartitioned into sub-bands. For example, a sub-band may cover 1.08 MHz,and there may be 1, 2, 4, 8 or 16 sub-bands. As mentioned above, inexamples that provide MTC communications using narrowband resources,corresponding narrowband bandwidth may be 200 kHz, which may include 180kHz of subcarriers and a 20 kHz guard band. In such examples, thenarrowband communications may occupy a single RB of an LTE systembandwidth, and there may be 12 sub-carriers.

A frame structure may be used to organize physical resources. A framemay be a 10 ms interval that may be further divided into 10 equallysized sub-frames. Each sub-frame may include two consecutive time slots.Each slot may include 6 or 7 OFDMA symbol periods. A resource elementconsists of one symbol period and one subcarrier (a 15 KHz frequencyrange). A resource block may contain 12 consecutive subcarriers in thefrequency domain and, for a normal cyclic prefix in each OFDM symbol, 7consecutive OFDM symbols in the time domain (1 slot), or 84 REs. SomeREs may include DL reference signals (DL-RS). The DL-RS may include aCRS, also referred to as a common reference signal, and a UE-specific RS(UE-RS). UE-RS may be transmitted on the resource blocks associated withphysical downlink shared channel (PDSCH). The number of bits carried byeach resource element may depend on the modulation scheme (theconfiguration of symbols that may be selected during each symbolperiod). Thus, the more resource blocks that a UE receives and thehigher the modulation scheme, the higher the data rate may be.

Some base stations 105 may utilize a portion of the available downlinkbandwidth to broadcast multimedia data to some or all UEs 115 within thecoverage area 110. For example, a wireless communication system may beconfigured to broadcast mobile TV content, or to multicast live eventcoverage to UEs 115 located near a live event such as a concert orsporting event. In some cases, this may enable more efficientutilization of the bandwidth. These base stations may be referred to asmultimedia broadcast multicast service (MBMS) or evolved multimediabroadcast multicast service (eMBMS) cells. In some cases, MBMS cells maybe grouped together in an MBSFN wherein the broadcast media istransmitted on the same frequency resources by each supporting cell.However, some UEs 115 in the coverage area may elect not to receive theMBMS data. If a base station 105 configures a subframe as a MBSFNsubframe, certain signals may not be transmitted in the subframe, suchas CRS transmissions. A UE 115 may receive the indication that thesubframe is a MBSFN subframe, and therefore may determine that a CRSwill not be present in the subframe.

As mentioned, the base station 105 may insert periodic pilot symbolssuch as CRS to aid UEs 115 in channel estimation and coherentdemodulation. CRS may include one of 504 different cell identities. Theymay be modulated using quadrature phase shift keying (QPSK) and powerboosted (e.g., transmitted at 6 dB higher than the surrounding dataelements) to make them resilient to noise and interference. CRS may beembedded in 4 to 16 REs in each resource block based on the number ofantenna ports or layers (up to 4) of the receiving UEs 115. In additionto CRS, which may be utilized by all UEs 115 in the coverage area 110 ofthe base station 105, a DMRS may be directed toward specific UEs 115 andmay be transmitted only on resource blocks assigned to those UEs 115.DMRS may include signals on 6 REs in each resource block in which theyare transmitted. The DM-RS for different antenna ports may each utilizethe same 6 REs, and may be distinguished using different orthogonalcover codes (e.g., masking each signal with a different combination of 1or −1 in different REs). In some cases, two sets of DMRS may betransmitted in adjoining REs. In some cases, additional referencesignals known as channel state information reference signals (CSI-RS)may be included to aid in generating channel state information (CSI). Onthe UL, a UE 115 may transmit a combination of periodic soundingreference signal (SRS) and uplink (UL) DMRS for link adaptation anddemodulation, respectively. DMRS transmissions may be precoded accordingto a particular precoding matrix index (PMI) for a particular UE 115. Insome examples, when transmitting narrowband communications, a basestation 105 may apply a same precoding matrix to transmissions in thesingle RB narrowband communication, which may allow a UE 115 to receivethe signal without relying on a CRS transmission.

Various aspects of the disclosure provide techniques for narrowbandcommunications in an LTE wireless communications network. In someaspects, narrowband MTC communications may be transmitted using a singleRB of a number of RBs used for wideband LTE communications. In order toprovide for efficient device discovery and synchronization usingnarrowband communications, some aspects provide a synchronizationsignal, such as a PSS or an SSS, that is transmitted within the singleresource block. The synchronization signal may be transmitted, forexample, using multiple OFDM symbols within the single RB. A CRS mayalso be present in the single resource block, which may puncture thesynchronization signal, in some examples. In other examples, thesynchronization signal may be mapped to non-CRS symbols of the singleresource block.

In certain aspects of the disclosure, a base station may transmit, and aUE may receive, an indication of a location of the single resource blockfor narrowband transmissions within a wideband region of the systembandwidth. The UE may identify one or more synchronization parametersfor receiving the narrowband transmissions based on the indication. TheUE may, in some examples, select a decoding technique for decoding basedon the identified frequency band of the narrowband transmissions, suchas based on whether the identified frequency band is within a widebandtransmission bandwidth or outside of the wideband transmissionbandwidth. In other aspects, a set of subcarriers may be identifiedwithin the narrowband region of the system bandwidth used to transmit aresource block, and a center-frequency subcarrier of the set ofsubcarriers identified. One or more other subcarriers of the set ofsubcarriers may be modified based on the identification of thecenter-frequency subcarrier, such as through frequency shifting or powerboosting, for example.

As shown herein, a UE 115 may include a UE narrowband communicationmodule 140 which may perform the various techniques described herein. Inone example, the UE narrowband communication module 140 may receive asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource blocktransmitted in the narrowband region, and synchronize one or moreparameters of transmissions in the narrowband region based at least inpart on the synchronization signal.

Also shown in FIG. 1 is that a BS 105 may include a base station (BS)narrowband communication module 145. The BS narrowband communicationmodule 145 may perform the various techniques described herein. Forexample, the BS narrowband communication module 145 may generate asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource block, andtransmit the synchronization signal in the narrowband region.

FIG. 2 illustrates an example of a wireless communications subsystem 200for downlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure. Wireless communications subsystem 200 may include a UE 115-aand base station 105-a, which may be examples of a UE 115 base station105 described with reference to FIG. 1.

In some examples, UE 115-a is an MTC device, such as a smart meter, thatmay communicate with base station 105-a using narrowband communicationsover the communication link 125-a. In order to perform device discoveryand synchronization, base station 105-a may generate a synchronizationsignal, such as a PSS and/or SSS, that may include two or more OFDMsymbols within a single resource block, and transmit the synchronizationsignal in the narrowband region. The UE 115-a may receive thesynchronization signal and synchronize one or more parameters oftransmissions in the narrowband region based thereon. In some examples,decoding of the synchronization signals may depend upon whether thenarrowband transmission is located within a transmission bandwidth of awideband transmission (e.g., a LTE RB in a wideband LTE transmission),or located outside of the wideband transmission bandwidth. In caseswhere the narrowband transmission is within the wideband transmissionbandwidth, the base station 105-a may identify a location of the RB andtransmit an indication of the location to the UE 115-a. Such anindication may include, in some examples, a total wideband bandwidth ofthe system bandwidth and a resource block index that indicates alocation of the single resource block. In other examples, the indicationmay simply indicate a RB offset from start of the wideband bandwidth.

FIG. 3 illustrates an example of a system bandwidth and various options300 for placement of a narrowband transmission resource block within asystem bandwidth that support downlink and synchronization techniquesfor narrowband wireless communications, in accordance with variousaspects of the present disclosure. Options 300 may be used by wirelessnetwork devices, such as MTC type UEs 115 and base stations 105described with reference to FIGS. 1-2. In some deployments, a number ofRBs 305 may be used for wideband transmissions between a base stationand various UEs. Narrowband MTC type UEs may be configured to receive asubset of the communications using a narrowband region of LTE systembandwidth 325, for example. In some instances, narrowband communicationsmay be transmitted in a guard band 310 of an LTE system, which may belocated outside of the LTE system bandwidth 325. In other examples, thenarrowband communications may be transmitted in configured RBs 315 fornarrowband transmissions, which may be signaled by a base station to UEsthat may be served by the base station. In further examples, narrowbandcommunications may be transmitted in a dedicated set of RBs 320 of LTEsystem bandwidth 325. These RBs 320 may be deployed in-band. In furtherexamples, narrowband communications may be transmitted in a frequencyband that may be allocated to communications of another radio accesstechnology, such as in a frequency band allocated for GSMcommunications. A UE that receives communications, according to variousaspects of the disclosure may be configured to identify a frequency bandof the narrowband communications and select one or more decoding andsynchronization techniques based on a particular frequency band.

Through the reuse of a LTE RB for narrowband communications, varioushigher layers of LTE systems, along with hardware of such systems, maybe utilized in an efficient manner without a significant amount ofadditional overhead. Such techniques may also avoid fragmentation (e.g.,a device could implement communications techniques that use differingamounts of transmission bandwidth). When using a narrowband signal thatoccupies a single RB, a UE may perform a cell search using only thenarrowband signal, and thus a UE might not know that a configured RB fornarrowband communications is placed inside the wideband LTE bandwidth325, or if the RB is transmitted in a standalone deployment in afrequency band that is not within the wideband LTE bandwidth 325.Furthermore, even when a single RB is reserved for narrowbandcommunications with LTE bandwidth 325, some legacy LTE signals may stillbe transmitted in this RB, such as CRS tones used by legacy UEs fortracking loops. Furthermore, legacy control regions (e.g., PDCCH) may bepresent in such a single RB for legacy UEs. In standaloneconfigurations, there is no need to transmit these signals, as legacyUEs would not be served in such configurations. In some aspects of thedisclosure, UEs may determine that narrowband communications are withina wideband system bandwidth, or outside of a wideband system bandwidth,and may process received signals accordingly. In some aspects, aunified, or similar, design is provided for both in-band narrowbandcommunications and standalone communications. Various aspects of thedisclosure, as will be discussed in more detail below, providesynchronization signal and PBCH techniques that may allow a UE toperform device discovery and synchronization using narrowbandtransmissions in multiple different types of deployments.

FIG. 4 illustrates an example of a resource element mapping 400 thatsupports downlink and synchronization techniques for narrowband wirelesscommunications, in accordance with various aspects of the presentdisclosure. Resource element mapping 400 may be used by wireless networkdevices, such as UEs 115 and base stations 105 described with referenceto FIGS. 1-2 that may operate using narrowband communications. Asmentioned above, for communications that are within a bandwidth ofwideband communications, various reference signals (e.g., CRS), may beconfigured to be transmitted in certain REs of certain RBs. Furthermore,certain synchronization signals (e.g., PSS and/or SSS) may be providedfor device discovery and synchronization.

In the example of FIG. 4, a subframe 405 may include a number of RBs,including a narrowband (NB) RB 410. In this example, CRS REs 415 may belocated in symbols 0, 4, 7, and 11 of a RB. In some examples, RBs 410-aand 410-b may be provided in consecutive subframes 405. Furthermore,PDCCH REs 420 may be provided in the first two symbols of RB 410.According to some examples, PSS REs 425 may be provided in multipleconsecutive OFDM symbols, and SSS REs 430 may be provided in multipleconsecutive OFDM symbols of a first RB 410-a. In such a manner, anentire synchronization signal may be contained in a single RB, and thusa UE that receives only the signal RB 410-a may perform device discoveryand synchronization when receiving narrowband transmissions that occupya single RB in wideband transmissions. As discussed above, CRS REs 415may be present in certain OFDM symbols, and in the example of FIG. 4,these CRS REs 415 puncture the PSS REs 425 and SSS REs 430. Suchpuncturing may create some additional interference in the PSS/SSSsynchronization signals. In other examples, a base station may configurethe PSS/SSS subframe that contains the first RB 410-a as a MBSFNsubframe, and thus no CRS will be present in that subframe. In someinstances, a subframe 410 may already be configured as a MBSFN subframe,and thus no CRS will be present in the transmissions without the basestation having to reconfigure the subframe 410. A second RB 410-b mayinclude PBCH REs 435, which may be transmitted using a DMRS, accordingto some examples, as will be discussed in more detail below.

In other examples, a base station may map synchronization signals suchthat they are not transmitted in OFDM symbols that include CRS REs. FIG.5 illustrates such an example of a resource element mapping 500 thatsupports downlink and synchronization techniques for narrowband wirelesscommunications, in accordance with various aspects of the presentdisclosure. Resource element mapping 500 may be used by wireless networkdevices, such as UEs 115 and base stations 105 described with referenceto FIGS. 1-2 that may operate using narrowband communications.

In the example of FIG. 5, a subframe 505 may include a number of RBs,including a narrowband RB 510. In this example, CRS REs 515 are againlocated in symbols 0, 4, 7, and 11 of RB 510. Furthermore, PDCCH REs 520may be provided in the first two symbols of RB 510. According to someexamples, PSS REs 525 may be mapped such that they are not transmittedin symbols that include CRS REs 515. In such a manner, an entiresynchronization signal may be contained in a single RB, and thus a UEthat receives only the signal RB 510 may perform device discovery andsynchronization when receiving narrowband transmissions that occupy asingle RB in wideband transmissions. IN a similar manner, SSS REs couldbe transmitted in a separate RB and mapped to avoid symbols that containCRS REs 515. In some examples, a different design for PSS/SSS isprovided for in-band and out-of-band narrowband communications, in whichin-band narrowband communications have synchronization signals that aremapped to avoid CRS REs, and in which standalone narrowbandcommunications have synchronization signals that occupy consecutive OFDMsymbols. Thus, a UE is able to know if the narrowband communications arein a standalone frequency band or are in-band after receiving thesynchronization signal.

FIG. 6 illustrates an example 600 of a narrowband region within atransmission bandwidth of a wideband transmission and a narrowbandregion in another allocated frequency band support downlink andsynchronization techniques for narrowband wireless communications, inaccordance with various aspects of the present disclosure. Example 600may be used by wireless network devices, such as UEs 115 and basestations 105 described with reference to FIGS. 1-2 that may operateusing narrowband communications.

In the example of FIG. 6, LTE system bandwidth 620 may include controlregion 605, a wideband data region 610, and first narrowband region615-a. A second narrowband region 615-b may be provided for standalonenarrowband communications, and may be located in some other bandwidth625, such as a bandwidth allocated for GSM communications, for example.

In some examples, first narrowband region 615-a may occupy a single RB(e.g., 12 subcarriers) of wideband data region 610. In one example,(e.g., for a 20 MHz carrier) wideband data region 610 may include 100RBs (1200 subcarriers). The particular narrowband region 615-a or 615-bmay be configured for narrowband communications based on variousdeployment parameters, such as the availability of one or more frequencybands that are outside of LTE system bandwidth 620, the usage of the LTEsystem bandwidth 620 by other devices, to name but two examples. In someexamples, a base station may provide an indication to UEs whether thenarrowband region 615-a or 615-b is within a wideband bandwidth. Such anindication may create some overhead (e.g., due to transmission onMIB/SIB), but enables some design options. For example, with knowledgeof whether the narrowband region 615-a or 615-b is within a widebandbandwidth may enable frequency hopping, in which base stations and UEsusing narrowband communication may achieve frequency diversity byretuning in both uplink and downlink. Further, such knowledge may enablethe re-use of CRS tones. For example, if a UE knows the position insidethe wideband bandwidth of the narrowband RB, the wideband CRS tones canbe re-used for tracking/demodulation. If no CRS are used in standalone(e.g. all channels and loops are based on DMRS), then the UE may benefitfrom the knowledge of whether CRS are present or not for rate matchingpurposes, for example.

In some examples, knowing the presence of CRS tones might be used forrate matching purposes. For example, a cell that does not have CRS mayuse the CRS tones for transmissions of data and control, whereas a cellthat has CRS transmission may rate match control and data around the CRStones. Additionally or alternatively, the base station may provideinformation about the number of CRS ports. For example, a base stationthat operates in standalone mode can signal to have 0 CRS ports. Forin-band deployments, the base station may signal the actual number ofCRS antenna ports (e.g., 1, 2 or 4). For guard band deployment, the basestation may signal the actual number of CRS antenna ports, or 0 CRSports. The information about the number of CRS ports may be broadcastedby the eNB. In one example, information about the number of CRS portscan be contained in MIB or SIB. In another example, information aboutthe number of CRS ports can be transmitted by scrambling the PBCH CRC bydifferent sequences depending on the number of antenna ports. In suchcases, the scrambling sequence used for 0 CRS ports may also imply thatthe deployment mode is standalone.

In some examples, a base station may provide an indication to UEs, whichmay include the wideband bandwidth of LTE system bandwidth 620, and theRB index of the narrowband region to be used inside the widebandbandwidth. If a 20 MHz bandwidth is assumed, the RB index of narrowbandregion 615-a may be signaled using 9 bits, which in some examples may bereduced to eight bits by removing some available RBs as options fornarrowband region 615-a. In other examples, a base station may simplysignal an offset, which may be signaled using seven bits (assuming 20MHz LTE system bandwidth 620). A UE may receive such an indication andidentify one or more synchronization parameters for receiving thenarrowband transmissions, and may generate a CRS sequence, in someexamples, based on the cell ID and a resource block offset valueincluded in the indication. In further examples, a base station mayprovide the indication through the presence or absence of CRS tones, andin some cases a number of transmit antennas, using one or two bits.After determining this information, a UE may rate match around CRStones, but may not be able to utilize CRS for loops or channelestimation. In some examples, signaling of whether narrowband region615-a is within LTE system bandwidth 620 may be included in MIB/SIBtransmissions.

As mentioned above, in some examples PBCH transmissions using narrowbandtransmissions may be transmitted, and some aspects of the disclosureprovide that a UE does not need to use CRS to demodulate such PBCHtransmissions. In some examples, PBCH transmissions may be DMRS based,and thus a UE receiving the transmissions does not need to receive a CRSto demodulate PBCH transmissions. In some examples, precoding(s) forPBCH transmissions may be fixed, so that after a MIB is decoded for thefirst time, the CRS tones can be reused for channel estimation by a UE.In other examples, PBCH transmissions may be transmitted in MBSFNsubframes, so no CRS tones are present. In certain examples, CRS tonesmay be inserted with an offset of zero, which may allow a UE to performenhanced tracking/demodulation. In further examples, PBCH decoding maydepend on the frequency band of the narrowband transmissions. Forexample, if the narrowband transmission frequency band is allocated toGSM spectrum, then a UE may determine that the narrowband transmissionis a standalone transmission outside of a wideband transmissionbandwidth, so CRS (or CRS+DMRS) can be used from the first acquisitionof PBCH transmissions. If the frequency band of the narrowbandtransmission allocated within an LTE system bandwidth, for example, thenthe UE may know that PBCH is transmitted using DMRS or in a MBSFNsubframe. This information can be pre-programmed in a UE, according tosome examples.

FIG. 7 illustrates an example 700 of a different center frequencysub-carriers for a wideband transmission and a narrowband transmission,in accordance with various aspects of the present disclosure. Example700 may be used by wireless network devices, such as UEs 115 and basestations 105 described with reference to FIGS. 1-2 that may operateusing narrowband communications.

In the example of FIG. 7, wideband transmissions 705 may be transmittedusing a number of subcarriers, with a center frequency, or DCsubcarrier, 720-a having a zero frequency offset Such a DC subcarrier710-a is not used for data transmissions, and both UEs and base stationsmay be configured such that the DC subcarrier 720-a is not used for datatransmissions. In narrowband transmissions 710, however, a MTC UE may beconfigured to receive narrowband communications, and a DC subcarrier720-b may be offset from DC subcarrier 720-a. Thus, for in-banddeployments, a narrowband UE receive DC subcarrier 720-b is not alignedwith the base station transmit DC subcarrier 720-a. Thus, for in-banddeployments DC leakage may eliminate one tone for RB, which implies that1/12 tones may not be used for data. For standalone deployments, such anoffset may not be present, although if only the center subcarrier is toremain unused, then the RB may be provided with 13 subcarriers (195 kHzin total bandwidth).

For in-band deployments, in some examples, a UE may simply lose the DCsubcarrier REs 720-b. In such examples, the UE may signal to the basestation that it is losing that carrier, and the base station may ratematch around DC subcarrier REs 720-b and power boost the other tones. Inother examples, the UE may apply a half-tone shift at the receive end,such that the DC leakage is split mainly between the two centersubcarriers. In further examples, for standalone deployment, the basestation may generate the digital waveform with an offset of half asubcarrier and adjust the transmitted local oscillator to take intoaccount that offset, in which case the DC impact will be mainly taken bythe center two subcarriers.

According to some examples, the waveform for the synchronization signalmay be generated to provide good cross-correlation properties. In someexamples, a PSS waveform may be generated using a Zadoff-Chu sequence.As discussed above, in some narrowband deployments a PSS may use 180kHz, and 6 OFDM symbols. For the OFDM symbols, with short CP, there willbe approximately 77 DFT samples. The next prime number is thus 79 forpurposes of a Zadoff-Chu sequence. FIGS. 8A-8C illustrate examples of asequence generation that supports downlink and synchronizationtechniques for narrowband wireless communications in accordance withvarious aspects of the present disclosure.

In the waveform generation process, according to some examples, alength-79 Zadoff-Chu sequence may be generated. Such a length-79Zadoff-Chu sequence is illustrated in the example 800 of FIG. 8A. Insome examples, the sequence may be differentially encoded. After thelength-79 Zadoff-Chu sequence is generated, the sequence is interpolatedusing length 822 inverse discrete Fourier transform (IDFT), to generatean oversampled time-domain waveform 820 of FIG. 8B (822 is the number ofsamples at 1.92 MHz). The oversampled time-domain waveform is then splitinto 6 parts of length 137 each. For each part, the first nine samplesmay discarded, for replacement by the corresponding CP. The remaining128 samples are pre-processed in the frequency domain in which (1) alength 128 FFT is applied, (2) windowing in frequency domain is appliedto keep only the 12 center subcarriers (FIG. 8C), and (3) a length 128IFFT is applied, to generate time domain signal 840. Following this,usual DFT processing may be performed, such as IDFT and CP addition.FIG. 9 illustrates an example 900 of auto-correlation properties of anexemplary sequence generated in accordance with FIGS. 8A-8C.

FIG. 10 illustrates an example of a process flow 1000 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Process flow1000 may include a UE 115-b and base station 105-b, which may beexamples of a UE 115 and base station 105 described with reference toFIGS. 1-2.

Initially, at block 1005, the base station 105-b may generate asynchronization signal, such as discussed above with respect to FIGS.1-9. At block 1010, the base station 105-b may optionally map thesynchronization signal to OFDM symbols. For example, the base station105-b may map the synchronization signal such that OFDM symbols thatinclude a CRS are not used for transmission of the synchronizationsignal. At block 1015, the base station 105-b may optionally configure asubframe used for synchronization signal transmission. For example, basestation 105-b may configure a subframe as a MBSFN subframe, such thatthe subframe will not include CRS transmissions. In another example,base station 105-b may map the synchronization signal to OFDM symbols ifoperating inside a wideband, and transmit the raw oversampledsynchronization signal (e.g., signal 820 of FIG. 8B) if operating instandalone mode. The base station 105-b may then transmit signal 1020 toUE 115-b.

At the UE 115-b, the synchronization signal may be received at block1025. At block 1030, the UE 115-b may identify a narrowband region ofthe transmission and an associated decoding technique. Such a narrowbandregion may be identified as an in-band region that is in-band withwideband transmissions, or as an out-of-band region, and decodingtechniques may be selected based on such an identification, as discussedabove with respect to FIGS. 1-9. At block 1035, the UE 115-b may decodethe received signal.

FIG. 11 illustrates an example of a process flow 1100 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Process flow1100 may include a UE 115-c and base station 105-c, which may beexamples of a UE 115 and base station 105 described with reference toFIG. 1-2, or 10.

Initially, at block 1105, the base station 105-c may identify anarrowband RB location, such as a location within a widebandtransmission bandwidth or in a separate standalone bandwidth, asdiscussed above. At block 1110, the base station 105-c may optionallyidentify a total wideband bandwidth and a RB offset within the widebandbandwidth. In other examples, the base station 105-c may identify a RBoffset without the total wideband bandwidth. At block 1115, the basestation 105-c may configure a MIB/SIB with the narrowband RBinformation. The base station 105-c may transmit the MIB/SIB 1120 to UE115-c. At block 1125, the UE 115-c may receive the MIB/SIB and identifysynchronization parameters, in a manner such as discussed above. Thebase station 105-c may then transmit narrowband signal 1130, and the UE115-c, at block 1135, may receive and decode the signal.

FIG. 12 illustrates an example of a process flow 1200 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Process flow1200 may include a UE 115-d and base station 105-d, which may beexamples of a UE 115 and base station 105 described with reference toFIG. 1-2, or 10-11.

Initially, at block 1205, the base station 105-d may generate a PBCHsignal. The base station 105-d may optionally, at block 1210, modulatethe PBCH signal using a DMRS, as discussed above with reference to FIGS.1-9. At block 1215, the base station 105-d may optionally configure asubframe to transmit the PBCH signal as a MBSFN subframe, also asdiscussed above. The base station 105-d may transmit PBCH signal 1220.The UE 115-d may identify a frequency band of the narrowbandtransmission, according to block 1225. At block 1230 the UE 115-d mayselect a decoding technique based on the identification of the frequencyband. At block 1235, the UE 115-d may decode the received signal, asdiscussed above with respect to FIGS. 1-9.

FIG. 13 illustrates an example of a process flow 1300 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Process flow1300 may include a UE 115-e and base station 105-e, which may beexamples of a UE 115 and base station 105 described with reference toFIG. 1-2, or 10-12. At block 1305, the base station 105-e may identify aDC subcarrier for a narrowband transmission. The base station 105-e maythen, at block 1310, modify other subcarriers (e.g., by rate matching orpower boosting), as discussed above with respect to FIGS. 1-9. The basestation 105-e may transmit narrowband signal 1320 to UE 115-e.Similarly, the UE 115-e may identify a DC subcarrier for a narrowbandtransmission, as indicated at block 1325. The UE 115-e may then, atblock 1330, modify processing of other subcarriers (e.g., by frequencyshifting or power boosting), as discussed above with respect to FIGS.1-9. The UE 115-e may receive narrowband transmission 1320, and decodethe received signal at block 1335.

FIG. 14 shows a block diagram of a wireless device 1400 configured fordownlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure. Wireless device 1400 may be an example of aspects of a UE115 described with reference to FIGS. 1-13. Wireless device 1400 mayinclude a receiver 1405, a narrowband communication module 140-a, or atransmitter 1415. The narrowband communication module 140-a may be anexample of the UE narrowband communication module 140 described withreference to FIG. 1. Wireless device 1400 may also include a processor.Each of these components may be in communication with each other.

The receiver 1405 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to downlink andsynchronization techniques for narrowband wireless communications,etc.). Information may be passed on to the narrowband communicationmodule 140-a, and to other components of wireless device 1400.

The narrowband communication module 140-a may receive a synchronizationsignal for device discovery, the synchronization signal comprising twoor more OFDM symbols within a single resource block transmitted in thenarrowband region, and synchronize one or more parameters oftransmissions in the narrowband region based at least in part on thesynchronization signal.

The transmitter 1415 may transmit signals received from other componentsof wireless device 1400. In some examples, the transmitter 1415 may becollocated with the receiver 1405 in a transceiver module. Thetransmitter 1415 may include a single antenna, or it may include aplurality of antennas.

FIG. 15 shows a block diagram of a wireless device 1500 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Wirelessdevice 1500 may be an example of aspects of a wireless device 1400 or aUE 115 described with reference to FIGS. 1-14. Wireless device 1500 mayinclude a receiver 1405-a, a narrowband communication module 140-b, or atransmitter 1415-a. Wireless device 1500 may also include a processor.Each of these components may be in communication with each other. Thenarrowband communication module 140-b may also include a synchronizationsignal module 1505, and a synchronization module 1510.

The receiver 1405-a may receive information which may be passed on tonarrowband communication module 140-b, and to other components ofwireless device 1500. The narrowband communication module 140-b mayperform the operations described with reference to FIG. 14. Thetransmitter 1415-a may transmit signals received from other componentsof wireless device 1500.

The synchronization signal module 1505 may receive a synchronizationsignal for device discovery, the synchronization signal comprising twoor more OFDM symbols within a single resource block transmitted in thenarrowband region as described with reference to FIGS. 2-13. In someexamples, the synchronization signal comprises one or more of a PSS or aSSS. In some examples, the generating the synchronization signalcomprises generating a sequence in a frequency domain or a time domainbased at least in part on a number of OFDM symbols in the singleresource block.

The synchronization module 1510 may synchronize one or more parametersof transmissions in the narrowband region based at least in part on thesynchronization signal as described with reference to FIGS. 2-13. Thesynchronization module 1510 may also identify one or moresynchronization parameters for receiving the narrowband transmissionsbased at least in part on the indication. In some examples, theidentifying the one or more synchronization parameters comprisesgenerating a CRS sequence based at least in part on the a cellidentification of a transmitter and a resource block offset valueincluded in the indication.

FIG. 16 shows a block diagram 1600 of a narrowband communication module140-c which may be a component of a wireless device 1400 or a wirelessdevice 1500 for downlink and synchronization techniques for narrowbandwireless communications in accordance with various aspects of thepresent disclosure. The narrowband communication module 140-c may be anexample of aspects of a narrowband communication module 140-a describedwith reference to FIGS. 14-15. The narrowband communication module 140-cmay include a synchronization signal module 1505-a, and asynchronization module 1510-a. Each of these modules may perform thefunctions described with reference to FIG. 15. The narrowbandcommunication module 140-c may also include a narrowband determinationmodule 1605, a time domain interpolation module 1610, a RB locationmodule 1615, a device discovery module 1620, a decoding technique module1625, a subcarrier identification module 1630, a center frequencyidentification module 1635, and a rate matching module 1640.

The narrowband determination module 1605 may determine whether thenarrowband region is within a bandwidth of one or more widebandtransmissions based at least in part of a format of the synchronizationsignal as described with reference to FIGS. 2-13. In some examples, thedetermining comprises identifying that the narrowband region may bewithin the bandwidth of one or more wideband transmissions in responseto the synchronization signal being formatted in consecutive OFDMsymbols within the single resource block. The narrowband determinationmodule 1605 may also identify that the narrowband region is outside ofthe bandwidth of one or more wideband transmissions in response to thesynchronization signal being formatted in one or more non-consecutiveOFDM symbols within the single resource block. The narrowbanddetermination module 1605 may also determine, based at least in part onthe identified frequency band, whether the narrowband region is within abandwidth of one or more wideband transmissions. In some examples, thedetermining whether the narrowband region may be within the bandwidth ofone or more wideband transmissions may be based at least in part on aradio access technology associated with the identified frequency band.In some examples, the determining whether the narrowband region may bewithin the bandwidth of one or more wideband transmissions comprisesdetermining that the narrowband region may be outside of the bandwidthof one or more wideband transmissions in response to the identifiedfrequency band being located in radio spectrum allocated to GSMcommunications. The narrowband determination module 1605 may alsodetermine that the narrowband region is within the bandwidth of one ormore wideband transmissions in response to the identified frequency bandbeing located in radio spectrum allocated to LTE communications.

The time domain interpolation module 1610 may generate an interpolatedtime domain version of the first sequence based at least in part on aset of samples of the first sequence as described with reference toFIGS. 2-13. In some examples, the generating the synchronization signalfurther comprises splitting the interpolated time domain version into aplurality of parts each having a duration of one OFDM symbol. The timedomain interpolation module 1610 may also identify a subset of samplesfor each part that correspond to a cyclic prefix associated with theassociated OFDM symbol. The time domain interpolation module 1610 mayalso remove the identified subset of samples for each part. The timedomain interpolation module 1610 may also insert a cyclic prefix intoeach part. In some examples, generating the synchronization signalfurther comprises windowing each OFDM symbol in the frequency domainsuch that only a subset of OFDM subcarriers carry the synchronizationsequence.

The RB location module 1615 may receive an indication of a location of asingle resource block for narrowband transmissions, the single resourceblock within the wideband region of the system bandwidth as describedwith reference to FIGS. 2-13. In some examples, the indication comprisesa total wideband bandwidth of the system bandwidth and a resource blockindex that indicates a location of the single resource block. In someexamples, the indication may be transmitted in one or more of a MIB or aSIB.

The device discovery module 1620 may identify a frequency band of thenarrowband region of the system bandwidth for transmission of a PBCHthat includes system information for device discovery as described withreference to FIGS. 2-13.

The decoding technique module 1625 may select a decoding technique fordecoding the PBCH based at least in part on the identified frequencyband of the narrowband region as described with reference to FIGS. 2-13.In some examples, selecting the decoding technique for decoding the PBCHcomprises selecting a CRS based decoding technique in response todetermining that the narrowband region may be outside of the bandwidthof one or more wideband transmissions. The decoding technique module1625 may also select a DMRS based decoding technique in response todetermining that the narrowband region is within the bandwidth of one ormore wideband transmissions.

The subcarrier identification module 1630 may identify a plurality ofsubcarriers within the narrowband region of the system bandwidth used totransmit a resource block as described with reference to FIGS. 2-13. Thesubcarrier identification module 1630 may also modify one or more othersubcarriers of the plurality of subcarriers based at least in part onthe identification of the center-frequency subcarrier. In some examples,the modifying one or more other subcarriers comprises receiving anindication that the center-frequency subcarrier may be to be unused fordata transmissions. In some examples, the modifying one or more othersubcarriers further comprises power boosting one or more of theplurality of subcarriers other than the center-frequency subcarrier. Insome examples, the modifying one or more other subcarriers comprisesapplying a frequency shift to one or more of the plurality ofsubcarriers other than the center-frequency subcarrier. In someexamples, the modifying one or more other subcarriers comprisesgenerating a digital waveform with an offset corresponding to afrequency shift of one-half of a subcarrier frequency bandwidth. Thesubcarrier identification module 1630 may also adjust a transmitoscillator based at least in part on the offset of the digital waveform.

The center frequency identification module 1635 may identify acenter-frequency subcarrier of the plurality of subcarriers used totransmit the resource block as described with reference to FIGS. 2-13.The rate matching module 1640 may rate match data transmissions aroundthe center-frequency subcarrier as described with reference to FIGS.2-13.

FIG. 17 shows a diagram of a system 1700 including a UE 115 configuredfor downlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure. System 1700 may include UE 115-f, which may be an example ofa wireless device 1400, a wireless device 1500, or a UE 115 describedwith reference to FIGS. 1, 2 and 10-16. UE 115-f may include anarrowband communication module 1710, which may be an example of anarrowband communication module 140 described with reference to FIGS. 1and 14-16. UE 115-f may also include a MTC module 1725 that may manageMTC communications. UE 115-f may also include components forbi-directional voice and data communications including components fortransmitting communications and components for receiving communications.For example, UE 115-f may communicate bi-directionally with base station105-f.

UE 115-f may also include a processor 1705, and memory 1715 (includingsoftware (SW)) 1720, a transceiver 1735, and one or more antenna(s)1740, each of which may communicate, directly or indirectly, with oneanother (e.g., via buses 1745). The transceiver 1735 may communicatebi-directionally, via the antenna(s) 1740 or wired or wireless links,with one or more networks, as described above. For example, thetransceiver 1735 may communicate bi-directionally with a base station105 or another UE 115. The transceiver 1735 may include a modem tomodulate the packets and provide the modulated packets to the antenna(s)1740 for transmission, and to demodulate packets received from theantenna(s) 1740. While UE 115-f may include a single antenna 1740, UE115-f may also have multiple antennas 1740 capable of concurrentlytransmitting or receiving multiple wireless transmissions.

The memory 1715 may include random access memory (RAM) and read onlymemory (ROM). The memory 1715 may store computer-readable,computer-executable software/firmware code 1720 including instructionsthat, when executed, cause the processor 1705 to perform variousfunctions described herein (e.g., downlink and synchronizationtechniques for narrowband wireless communications, etc.). Alternatively,the software/firmware code 1720 may not be directly executable by theprocessor 1705 but cause a computer (e.g., when compiled and executed)to perform functions described herein. The processor 1705 may include anintelligent hardware device, (e.g., a central processing unit (CPU), amicrocontroller, an application specific integrated circuit (ASIC),etc.)

FIG. 18 shows a block diagram of a wireless device 1800 configured fordownlink and synchronization techniques for narrowband wirelesscommunications in accordance with various aspects of the presentdisclosure. Wireless device 1800 may be an example of aspects of a basestation 105 described with reference to FIGS. 1-17. Wireless device 1800may include a receiver 1805, a base station narrowband communicationmodule 145-a, or a transmitter 1815. The base station narrowbandcommunication module 145-a may be an example of a base stationnarrowband communication module 145 described with reference to FIG. 1.Wireless device 1800 may also include a processor. Each of thesecomponents may be in communication with each other.

The receiver 1805 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to downlink andsynchronization techniques for narrowband wireless communications,etc.). Information may be passed on to the base station narrowbandcommunication module 145-a, and to other components of wireless device1800.

The base station narrowband communication module 145-a may generate asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource block, andtransmit the synchronization signal in the narrowband region.

The transmitter 1815 may transmit signals received from other componentsof wireless device 1800. In some examples, the transmitter 1815 may becollocated with the receiver 1805 in a transceiver module. Thetransmitter 1815 may include a single antenna, or it may include aplurality of antennas.

FIG. 19 shows a block diagram of a wireless device 1900 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Wirelessdevice 1900 may be an example of aspects of a wireless device 1800 or abase station 105 described with reference to FIGS. 1-18.

Wireless device 1900 may include a receiver 1805-a, a base stationnarrowband communication module 145-b, or a transmitter 1815-a. Wirelessdevice 1900 may also include a processor. Each of these components maybe in communication with each other. The base station narrowbandcommunication module 145-b may also include a synchronization signalgeneration module 1905, a narrowband synchronization signal module 1910,a narrowband region location module 1915, and a PBCH module 1920.

The receiver 1805-a may receive information which may be passed on tobase station narrowband communication module 145-b, and to othercomponents of wireless device 1900. The base station narrowbandcommunication module 145-b may perform the operations described withreference to FIG. 18. The transmitter 1815-a may transmit signalsreceived from other components of wireless device 1900.

The synchronization signal generation module 1905 may generate asynchronization signal for device discovery, the synchronization signalcomprising two or more OFDM symbols within a single resource block asdescribed with reference to FIGS. 2-13. In some examples, thesynchronization signal comprises one or more of a PSS or a SSS.

The narrowband synchronization signal module 1910 may transmit thesynchronization signal in the narrowband region as described withreference to FIGS. 2-13. In some examples, the synchronization signalmay be transmitted in a set of contiguous OFDM symbols. In someexamples, the transmission of the synchronization signal in thenarrowband region comprises transmitting the synchronization signal in asubframe previously configured as an MBSFN subframe. The narrowbandsynchronization signal module 1910 may also identify whether thenarrowband region is within a bandwidth of one or more widebandtransmissions. The narrowband synchronization signal module 1910 mayalso transmit the synchronization signal using the selected OFDMsymbols.

The narrowband region location module 1915 may identify a location ofthe narrowband region of the system bandwidth as a single resource blockwithin a wideband region of the system bandwidth as described withreference to FIGS. 2-13.

The PBCH module 1920 may generate a PBCH signal for transmission ofsystem information for device discovery in the narrowband region asdescribed with reference to FIGS. 2-13. The PBCH module 1920 may alsomodulate the PBCH signal based at least in part on a DMRS. The PBCHmodule 1920 may also transmit the modulated PBCH signal in thenarrowband region. The PBCH module 1920 may also generate a PBCH signalfor transmission of system information for device discovery, the PBCHsignal included in a resource block to be transmitted in the narrowbandregion. The PBCH module 1920 may also transmit the PBCH signal in theMBSFN subframe.

FIG. 20 shows a block diagram 2000 of a base station narrowbandcommunication module 145-c which may be a component of a wireless device1800 or a wireless device 1900 for downlink and synchronizationtechniques for narrowband wireless communications in accordance withvarious aspects of the present disclosure. The base station narrowbandcommunication module 145-c may be an example of aspects of a basestation narrowband communication module 145-a described with referenceto FIGS. 18-19. The base station narrowband communication module 145-cmay include a synchronization signal generation module 1905-a, anarrowband synchronization signal module 1910-a, a narrowband regionlocation module 1915-a, and a PBCH module 1920-a. Each of these modulesmay perform the functions described with reference to FIG. 19. The basestation narrowband communication module 145-c may also include a CRSmodule 2005, a CRS symbol identification module 2010, a symbol mappingmodule 2015, a MBSFN module 2020, a narrowband indication module 2025,and a PMI module 2030.

The CRS module 2005 may transmit a CRS using one or more REs thatpuncture the set of contiguous OFDM symbols as described with referenceto FIGS. 2-13. The CRS module 2005, in some examples, may transmit a CRSin one or more of the modulated PBCH signal or the other transmissionsin the narrowband region of the system bandwidth, the CRS for use inchannel estimation be one or more receivers as described with referenceto FIGS. 2-13. The base station CRS module 2005 may also transmit a CRSin the resource block. In some examples, the CRS may be generatedassuming a resource block offset of zero. In some examples, the CRS maybe transmitted in one or more OFDM symbols within the resource block,and wherein the one or more OFDM symbols have a fixed offset within theresource block.

The CRS symbol identification module 2010 may identify one or more OFDMsymbols within the single resource block as CRS OFDM symbols thatinclude one or more CRS REs as described with reference to FIGS. 2-13.The symbol mapping module 2015 may map the OFDM symbols that contain thesynchronization signal to non-CRS OFDM symbols as described withreference to FIGS. 2-13. The MBSFN module 2020 may configure a subframethat includes the synchronization signal as an MBSFN subframe asdescribed with reference to FIGS. 2-13. The MBSFN module 2020 may alsoidentify a subframe that includes the resource block as a MBSFNsubframe.

The narrowband indication module 2025 may indicate to one or morereceivers whether the narrowband region is within the bandwidth of oneor more wideband transmissions as described with reference to FIGS.2-13. In some examples, the indicating to one or more receivers whetherthe narrowband region may be within the bandwidth of one or morewideband transmissions comprises selecting OFDM symbols within thesingle resource block for transmission of the based at least in part onwhether the narrowband region may be within the bandwidth of one or morewideband transmissions. The narrowband indication module 2025 may alsotransmit an indication of the location of the single resource blockwithin the wideband region of the system bandwidth. In some examples,the indication comprises a total wideband bandwidth of the systembandwidth and a resource block index that indicates a location of thesingle resource block. In some examples, the indication comprises aresource block offset from start of a wideband bandwidth of the systembandwidth. In some examples, the indication comprises one or more CRSREs included in the single resource block. In some examples, theindication may be transmitted in one or more of a MIB or a SIB.

The PMI module 2030 may be configured such that the modulating the PBCHsignal may include selecting a precoding matrix for transmission of themodulated PBCH signal as described with reference to FIGS. 2-13. The PMImodule 2030 may also use the selected precoding matrix for othertransmissions in the narrowband region on the system bandwidth.

FIG. 21 shows a diagram of a system 2100 including a base station 105configured for downlink and synchronization techniques for narrowbandwireless communications in accordance with various aspects of thepresent disclosure. System 2100 may include base station 105-g, whichmay be an example of a wireless device 1800, a wireless device 1900, ora base station 105 described with reference to FIGS. 1, 2 and 18-20.Base Station 105-g may include a base station narrowband communicationmodule 2110, which may be an example of a base station narrowbandcommunication module 145-a described with reference to FIGS. 18-20. BaseStation 105-g may also include components for bi-directional voice anddata communications including components for transmitting communicationsand components for receiving communications. For example, base station105-g may communicate bi-directionally with UE 115-g or UE 115-h.

In some cases, the base station 105-g may have one or more wiredbackhaul links. The base station 105-g may have a wired backhaul link(e.g., S1 interface, etc.) to the core network 130. The base station105-g may also communicate with other base stations 105, such as thebase station 105-h and the base station 105-i via inter-base stationbackhaul links (e.g., an X2 interface). Each of the base stations 105may communicate with UEs 115 using the same or different wirelesscommunications technologies. In some cases, the base station 105-g maycommunicate with other base stations such as 105-h or 105-i utilizingthe base station communication module 2125. In some examples, the basestation communication module 2125 may provide an X2 interface within anLTE/LTE-A wireless communication network technology to providecommunication between some of the base stations 105. In some examples,the base station 105-g may communicate with other base stations throughthe core network 130. In some cases, the base station 105-g maycommunicate with the core network 130 through the network communicationsmodule 2130.

The base station 105-g may include a processor 2105, memory 2115(including software (SW)2120), a transceiver 2135, and antenna(s) 2140,which each may be in communication, directly or indirectly, with oneanother (e.g., over the bus system 2145). The transceivers 2135 may beconfigured to communicate bi-directionally, via the antenna(s) 2140,with the UEs 115, which may be multi-mode devices. The transceiver 2135(or other components of the base station 105-g) may also be configuredto communicate bi-directionally, via the antennas 2140, with one or moreother base stations. The transceiver 2135 may include a modem configuredto modulate the packets and provide the modulated packets to theantennas 2140 for transmission, and to demodulate packets received fromthe antennas 2140. The base station 105-g may include multipletransceivers 2135, each with one or more associated antennas 2140. Thetransceiver may be an example of a combined receiver 1805 andtransmitter 1815 of FIG. 18.

The memory 2115 may include RAM and ROM. The memory 2115 may also storecomputer-readable, computer-executable software code 2120 containinginstructions that are configured to, when executed, cause the processor2110 to perform various functions described herein (e.g., downlink andsynchronization techniques for narrowband wireless communications,selecting coverage enhancement techniques, call processing, databasemanagement, message routing, etc.). Alternatively, the software 2120 maynot be directly executable by the processor 2105 but be configured tocause the computer, e.g., when compiled and executed, to performfunctions described herein. The processor 2105 may include anintelligent hardware device, e.g., a CPU, a microcontroller, an ASIC,etc. The processor 2105 may include various special purpose processorssuch as encoders, queue processing modules, base band processors, radiohead controllers, digital signal processor (DSPs), and the like.

The base station communications module 2125 may manage communicationswith other base stations 105. In some cases, a communications managementmodule may include a controller or scheduler for controllingcommunications with UEs 115 in cooperation with other base stations 105.For example, the base station communications module 2125 may coordinatescheduling for transmissions to UEs 115 for various interferencemitigation techniques such as beamforming or joint transmission.

The components of the wireless device 1400, the wireless device 1500,and the narrowband communication module 140-a may, individually orcollectively, be implemented with at least one ASIC adapted to performsome or all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on at least one IC. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, a fieldprogrammable gate array (FPGA), or another semi-custom IC), which may beprogrammed in any manner known in the art. The functions of each unitmay also be implemented, in whole or in part, with instructions embodiedin a memory, formatted to be executed by one or more general orapplication-specific processors.

FIG. 22 shows a flowchart illustrating a method 2200 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2200 may be implemented by a UE 115 or itscomponents as described with reference to FIGS. 1-21. For example, theoperations of method 2200 may be performed by the narrowbandcommunication module 140 as described with reference to FIGS. 1 and14-17. In some examples, a UE 115 may execute a set of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects ofthe functions described below using special-purpose hardware.

At block 2205, the UE 115 may receive a synchronization signal fordevice discovery, the synchronization signal comprising two or more OFDMsymbols within a single resource block transmitted in the narrowbandregion as described with reference to FIGS. 2-13. In certain examples,the operations of block 2205 may be performed by the synchronizationsignal module 1505 as described with reference to FIG. 15.

At block 2210, the UE 115 may synchronize one or more parameters oftransmissions in the narrowband region based at least in part on thesynchronization signal as described with reference to FIGS. 2-13. Incertain examples, the operations of block 2210 may be performed by thesynchronization module 1510 as described with reference to FIG. 15.

FIG. 23 shows a flowchart illustrating a method 2300 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2300 may be implemented by a UE 115 or itscomponents as described with reference to FIGS. 1-21. For example, theoperations of method 2300 may be performed by the narrowbandcommunication module 140 as described with reference to FIGS. 1 and14-17. In some examples, a UE 115 may execute a set of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects ofthe functions described below using special-purpose hardware. The method2300 may also incorporate aspects of method 2200 of FIG. 22.

At block 2305, the UE 115 may receive an indication of a location of asingle resource block for narrowband transmissions, the single resourceblock within the wideband region of the system bandwidth as describedwith reference to FIGS. 2-13. In certain examples, the operations ofblock 2305 may be performed by the RB location module 1615 as describedwith reference to FIG. 16.

At block 2310, the UE 115 may identify one or more synchronizationparameters for receiving the narrowband transmissions based at least inpart on the indication as described with reference to FIGS. 2-13. Incertain examples, the operations of block 2310 may be performed by thesynchronization module 1510 as described with reference to FIG. 15.

FIG. 24 shows a flowchart illustrating a method 2400 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2400 may be implemented by a UE 115 or itscomponents as described with reference to FIGS. 1-21. For example, theoperations of method 2400 may be performed by the narrowbandcommunication module 140 as described with reference to FIGS. 1 and14-17. In some examples, a UE 115 may execute a set of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects ofthe functions described below using special-purpose hardware. The method2400 may also incorporate aspects of methods 2200, and 2300 of FIGS.22-23.

At block 2405, the UE 115 may identify a frequency band of thenarrowband region of the system bandwidth for transmission of a PBCHthat includes system information for device discovery as described withreference to FIGS. 2-13. In certain examples, the operations of block2405 may be performed by the device discovery module 1620 as describedwith reference to FIG. 16.

At block 2410, the UE 115 may select a decoding technique for decodingthe PBCH based at least in part on the identified frequency band of thenarrowband region as described with reference to FIGS. 2-13. In certainexamples, the operations of block 2410 may be performed by the decodingtechnique module 1625 as described with reference to FIG. 16.

FIG. 25 shows a flowchart illustrating a method 2500 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2500 may be implemented by a UE 115 or itscomponents as described with reference to FIGS. 1-21. For example, theoperations of method 2500 may be performed by the narrowbandcommunication module 140 as described with reference to FIGS. 1 and14-17. In some examples, a UE 115 may execute a set of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects ofthe functions described below using special-purpose hardware. The method2500 may also incorporate aspects of methods 2200, 2300, and 2400 ofFIGS. 22-24.

At block 2505, the UE 115 may identify a plurality of subcarriers withinthe narrowband region of the system bandwidth used to transmit aresource block as described with reference to FIGS. 2-13. In certainexamples, the operations of block 2505 may be performed by thesubcarrier identification module 1630 as described with reference toFIG. 16.

At block 2510, the UE 115 may identify a center-frequency subcarrier ofthe plurality of subcarriers used to transmit the resource block asdescribed with reference to FIGS. 2-13. In certain examples, theoperations of block 2510 may be performed by the center frequencyidentification module 1635 as described with reference to FIG. 16.

At block 2515, the UE 115 may modify one or more other subcarriers ofthe plurality of subcarriers based at least in part on theidentification of the center-frequency subcarrier as described withreference to FIGS. 2-13. In certain examples, the operations of block2515 may be performed by the subcarrier identification module 1630 asdescribed with reference to FIG. 16.

FIG. 26 shows a flowchart illustrating a method 2600 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2600 may be implemented by a base station 105 orits components as described with reference to FIGS. 1-21. For example,the operations of method 2600 may be performed by the base stationnarrowband communication module 145 as described with reference to FIGS.1 and 18-21. In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the base station 105 toperform the functions described below. Additionally or alternatively,the base station 105 may perform aspects of the functions describedbelow using special-purpose hardware. The method 2600 may alsoincorporate aspects of methods 2200, 2300, 2400, and 2500 of FIGS.22-25.

At block 2605, the base station 105 may generate a synchronizationsignal for device discovery, the synchronization signal comprising twoor more OFDM symbols within a single resource block as described withreference to FIGS. 2-13. In certain examples, the operations of block2605 may be performed by the synchronization signal generation module1905 as described with reference to FIG. 19.

At block 2610, the base station 105 may transmit the synchronizationsignal in the narrowband region as described with reference to FIGS.2-13. In certain examples, the operations of block 2610 may be performedby the narrowband synchronization signal module 1910 as described withreference to FIG. 19.

FIG. 27 shows a flowchart illustrating a method 2700 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2700 may be implemented by a base station 105 orits components as described with reference to FIGS. 1-21. For example,the operations of method 2700 may be performed by the base stationnarrowband communication module 145 as described with reference to FIGS.1 and 18-21. In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the base station 105 toperform the functions described below. Additionally or alternatively,the base station 105 may perform aspects of the functions describedbelow using special-purpose hardware. The method 2700 may alsoincorporate aspects of methods 2200, 2300, 2400, 2500, and 2600 of FIGS.22-26.

At block 2705, the base station 105 may identify a location of thenarrowband region of the system bandwidth as a single resource blockwithin a wideband region of the system bandwidth as described withreference to FIGS. 2-13. In certain examples, the operations of block2705 may be performed by the narrowband region location module 1915 asdescribed with reference to FIG. 19.

At block 2710, the base station 105 may transmit an indication of thelocation of the single resource block within the wideband region of thesystem bandwidth as described with reference to FIGS. 2-13. In certainexamples, the operations of block 2710 may be performed by thenarrowband indication module 2025 as described with reference to FIG.20.

FIG. 28 shows a flowchart illustrating a method 2800 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2800 may be implemented by a base station 105 orits components as described with reference to FIGS. 1-21. For example,the operations of method 2800 may be performed by the base stationnarrowband communication module 145 as described with reference to FIGS.1 and 18-21. In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the base station 105 toperform the functions described below. Additionally or alternatively,the base station 105 may perform aspects of the functions describedbelow using special-purpose hardware. The method 2800 may alsoincorporate aspects of methods 2200, 2300, 2400, 2500, 2600, and 2700 ofFIGS. 22-27.

At block 2805, the base station 105 may generate a PBCH signal fortransmission of system information for device discovery in thenarrowband region as described with reference to FIGS. 2-13. In certainexamples, the operations of block 2805 may be performed by the PBCHmodule 1920 as described with reference to FIG. 19.

At block 2810, the base station 105 may modulate the PBCH signal basedat least in part on a DMRS as described with reference to FIGS. 2-13. Incertain examples, the operations of block 2810 may be performed by thePBCH module 1920 as described with reference to FIG. 19.

At block 2815, the base station 105 may transmit the modulated PBCHsignal in the narrowband region as described with reference to FIGS.2-13. In certain examples, the operations of block 2815 may be performedby the PBCH module 1920 as described with reference to FIG. 19.

FIG. 29 shows a flowchart illustrating a method 2900 for downlink andsynchronization techniques for narrowband wireless communications inaccordance with various aspects of the present disclosure. Theoperations of method 2900 may be implemented by a base station 105 orits components as described with reference to FIGS. 1-21. For example,the operations of method 2900 may be performed by the base stationnarrowband communication module 145 as described with reference to FIGS.1 and 18-21. In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the base station 105 toperform the functions described below. Additionally or alternatively,the base station 105 may perform aspects of the functions describedbelow using special-purpose hardware. The method 2900 may alsoincorporate aspects of methods 2200, 2300, 2400, 2500, 2600, 2700, and2800 of FIGS. 22-28.

At block 2905, the base station 105 may generate a PBCH signal fortransmission of system information for device discovery, the PBCH signalincluded in a resource block to be transmitted in the narrowband regionas described with reference to FIGS. 2-13. In certain examples, theoperations of block 2905 may be performed by the PBCH module 1920 asdescribed with reference to FIG. 19.

At block 2910, the base station 105 may identify a subframe thatincludes the resource block as a MBSFN subframe as described withreference to FIGS. 2-13. In certain examples, the operations of block2910 may be performed by the MBSFN module 2020 as described withreference to FIG. 20.

At block 2915, the base station 105 may transmit the PBCH signal in theMBSFN subframe as described with reference to FIGS. 2-13. In certainexamples, the operations of block 2915 may be performed by the PBCHmodule 1920 as described with reference to FIG. 19.

Thus, methods 2200, 2300, 2400, 2500, 2600, 2700, 2800, and 2900 mayprovide for downlink and synchronization techniques for narrowbandwireless communications. It should be noted that methods 2200, 2300,2400, 2500, 2600, 2700, 2800, and 2900 describe possible implementation,and that the operations and the steps may be rearranged or otherwisemodified such that other implementations are possible. In some examples,aspects from two or more of the methods 2200, 2300, 2400, 2500, 2600,2700, 2800, and 2900 may be combined.

The description herein provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate.Also, features described with respect to some examples may be combinedin other examples.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, single carrierfrequency division multiple access (SC-FDMA), and other systems. Theterms “system” and “network” are often used interchangeably. A CDMAsystem may implement a radio technology such as CDMA2000, UniversalTerrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95,and IS-856 standards. IS-2000 Releases 0 and A are commonly referred toas CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as the GSM. An OFDMA system mayimplement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications system (UMTS). 3GPP LTE and LTE-a are new releases ofUniversal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA,E-UTRA, Universal Mobile Telecommunications System (UMTS), LTE, LTE-a,and the GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description herein, however, describes anLTE system for purposes of example, and LTE terminology is used in muchof the description above, although the techniques are applicable beyondLTE applications.

In LTE/LTE-a networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-a network in which different typesof eNBs provide coverage for various geographical regions. For example,each eNB or base station may provide communication coverage for a macrocell, a small cell, or other types of cell. The term “cell” is a 3GPPterm that can be used to describe a base station, a carrier or componentcarrier associated with a base station, or a coverage area (e.g.,sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up only a portionof the coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies). Each modulated signal may be sent ona different sub-carrier and may carry control information (e.g.,reference signals, control channels, etc.), overhead information, userdata, etc. The communication links described herein (e.g., communicationlinks 125 of FIG. 1) may transmit bidirectional communications usingfrequency division duplex (FDD) (e.g., using paired spectrum resources)or TDD operation (e.g., using unpaired spectrum resources). Framestructures may be defined for frequency division duplex (FDD) (e.g.,frame structure type 1) and TDD (e.g., frame structure type 2).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a digital signal processor (DSP) and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication in a systemthat supports operation in a narrowband region of a system bandwidth,comprising: identifying a plurality of subcarriers within the narrowbandregion of the system bandwidth used to transmit a resource block;identifying a center-frequency subcarrier of the plurality ofsubcarriers used to transmit the resource block; and modifying one ormore other subcarriers of the plurality of subcarriers based at least inpart on the identification of the center-frequency subcarrier.
 2. Themethod of claim 1, wherein the modifying one or more other subcarrierscomprises: receiving an indication that the center-frequency subcarrieris to be unused for data transmissions.
 3. The method of claim 2,wherein the modifying one or more other subcarriers further comprises:rate matching data transmissions around the center-frequency subcarrier.4. The method of claim 2, wherein the modifying one or more othersubcarriers further comprises: power boosting one or more of theplurality of subcarriers other than the center-frequency subcarrier. 5.The method of claim 2, wherein the indication is received in one or moreof a master information block (MIB) or a system information block (SIB).6. The method of claim 1, wherein the modifying one or more othersubcarriers comprises: applying a frequency shift to one or more of theplurality of subcarriers other than the center-frequency subcarrier. 7.The method of claim 1, wherein the modifying one or more othersubcarriers comprises: generating a digital waveform with an offsetcorresponding to a frequency shift of one-half of a subcarrier frequencybandwidth; and adjusting a transmit oscillator based at least in part onthe offset of the digital waveform.
 8. The method of claim 1, furthercomprising: receiving a narrowband transmission at the resource blockbased at least in part on identifying the center-frequency subcarrier ofthe plurality of subcarriers; and decoding the narrowband transmission.9. An apparatus for wireless communication in a system that supportsoperation in a narrowband region of a system bandwidth, comprising: aprocessor; memory coupled with the processor; and instructions stored inthe memory and operable, when executed by the processor, to cause theapparatus to: identify a plurality of subcarriers within the narrowbandregion of the system bandwidth used to transmit a resource block;identify a center-frequency subcarrier of the plurality of subcarriersused to transmit the resource block; and modify one or more othersubcarriers of the plurality of subcarriers based at least in part onthe identification of the center-frequency subcarrier.
 10. The apparatusof claim 9, wherein the instructions to modify the one or more othersubcarriers further comprises instructions stored in the memory andoperable, when executed by the processor, to cause the apparatus to:receive an indication that the center-frequency subcarrier is to beunused for data transmissions.
 11. The apparatus of claim 10, whereinthe instructions to modify the one or more other subcarriers furthercomprises instructions stored in the memory and operable, when executedby the processor, to cause the apparatus to: rate match datatransmissions around the center-frequency subcarrier.
 12. The apparatusof claim 10, wherein the instructions to modify the one or more othersubcarriers further comprises instructions stored in the memory andoperable, when executed by the processor, to cause the apparatus to:power boost one or more of the plurality of subcarriers other than thecenter-frequency subcarrier.
 13. The apparatus of claim 9, wherein theindication is received in one or more of a master information block(MIB) or a system information block (SIB).
 14. The apparatus of claim 9,wherein the instructions to modify the one or more other subcarriersfurther comprises instructions stored in the memory and operable, whenexecuted by the processor, to cause the apparatus to: apply a frequencyshift to one or more of the plurality of subcarriers other than thecenter-frequency subcarrier.
 15. The apparatus of claim 9, wherein theinstructions to modify the one or more other subcarriers furthercomprises instructions stored in the memory and operable, when executedby the processor, to cause the apparatus to: generate a digital waveformwith an offset corresponding to a frequency shift of one-half of asubcarrier frequency bandwidth; and adjust a transmit oscillator basedat least in part on the offset of the digital waveform.
 16. Theapparatus of claim 9, wherein the instructions further compriseinstructions stored in the memory and operable, when executed by theprocessor, to cause the apparatus to: receive a narrowband transmissionat the resource block based at least in part on identifying thecenter-frequency subcarrier of the plurality of subcarriers; and decodethe narrowband transmission.
 17. A non-transitory computer-readablemedium storing code for wireless communication in a system that supportsoperation in a narrowband region of a system bandwidth, the codecomprising instructions executable to: identify a plurality ofsubcarriers within the narrowband region of the system bandwidth used totransmit a resource block; identify a center-frequency subcarrier of theplurality of subcarriers used to transmit the resource block; and modifyone or more other subcarriers of the plurality of subcarriers based atleast in part on the identification of the center-frequency subcarrier.18. The non-transitory computer-readable medium of claim 17, wherein theinstructions executable to modify the one or more other subcarriersfurther comprises instructions to: receive an indication that thecenter-frequency subcarrier is to be unused for data transmissions. 19.The non-transitory computer-readable medium of claim 18, wherein theinstructions executable to modify the one or more other subcarriersfurther comprises instructions to: rate match data transmissions aroundthe center-frequency subcarrier.
 20. The non-transitorycomputer-readable medium of claim 18, wherein the instructionsexecutable to modify the one or more other subcarriers further comprisesinstructions to: power boost one or more of the plurality of subcarriersother than the center-frequency subcarrier.
 21. The non-transitorycomputer-readable medium of claim 17, wherein the indication is receivedin one or more of a master information block (MIB) or a systeminformation block (SIB).
 22. The non-transitory computer-readable mediumof claim 17, wherein the instructions executable to modify the one ormore other subcarriers further comprises instructions to: apply afrequency shift to one or more of the plurality of subcarriers otherthan the center-frequency subcarrier.
 23. The non-transitorycomputer-readable medium of claim 17, wherein the instructionsexecutable to modify the one or more other subcarriers further comprisesinstructions to: generate a digital waveform with an offsetcorresponding to a frequency shift of one-half of a subcarrier frequencybandwidth; and adjust a transmit oscillator based at least in part onthe offset of the digital waveform.
 24. The non-transitorycomputer-readable medium of claim 17, wherein the instructions furthercause the apparatus to: receive a narrowband transmission at theresource block based at least in part on identifying thecenter-frequency subcarrier of the plurality of subcarriers; and decodethe narrowband transmission.
 25. An apparatus for wireless communicationin a system that supports operation in a narrowband region of a systembandwidth, comprising: means for identifying a plurality of subcarrierswithin the narrowband region of the system bandwidth used to transmit aresource block; means for identifying a center-frequency subcarrier ofthe plurality of subcarriers used to transmit the resource block; andmeans for modifying one or more other subcarriers of the plurality ofsubcarriers based at least in part on the identification of thecenter-frequency subcarrier.
 26. The apparatus of claim 1, wherein themeans for modifying one or more other subcarriers comprises: means forreceiving an indication that the center-frequency subcarrier is to beunused for data transmissions; and means for rate matching datatransmissions around the center-frequency subcarrier.
 27. The apparatusof claim 2, wherein the means for modifying one or more othersubcarriers further comprises: means for power boosting one or more ofthe plurality of subcarriers other than the center-frequency subcarrier.28. The apparatus of claim 2, wherein the indication is received in oneor more of a master information block (MIB) or a system informationblock (SIB).
 29. The apparatus of claim 1, wherein the means formodifying one or more other subcarriers comprises: means for applying afrequency shift to one or more of the plurality of subcarriers otherthan the center-frequency subcarrier.
 30. The apparatus of claim 1,wherein the means for modifying one or more other subcarriers comprises:means for generating a digital waveform with an offset corresponding toa frequency shift of one-half of a subcarrier frequency bandwidth; andmeans for adjusting a transmit oscillator based at least in part on theoffset of the digital waveform.